Information recording and developing apparatus and method



7, 1964 w. E. GLENN, JR., ETAL 3, ,9

INFORMATION RECORDING AND DEVELOPING APPARATUS AND METHOD Filed Sept. 20. 1961 F S 5% i N m? @m 8 n w? MM? m .a zw fm R /0 & wdm, o6 w\ \mvl United States Patent 3,116,962 INIFGRMATEON RECURDENG ANE) DEVELGPING APPARATUS AND METH'UD William E. Glenn, Jim, cheneetady, and John L.

Henhes, .lr., Londonviile, N.Y., assignors to General Eieetric Company, a corporation oft New York Filed Sept. 20, 1961, Ser. No. 139,460 4 Claims. (Cl. 34677) The present invention relates to improved apparatus and method for recording information particularly on a thermoplastic medium. The invention relates particularly to improved cooling of the recording medium after it has been heated and subjected to the information containing electric charge pattern.

In copending Glenn application Serial No. 8,842, filed February 15, 1960, entitled Method and Apparatus for Recording, and in application Serial No. 84,424, filed January 23, 1961, as a division of said application Serial No. 8,842 entitled Method for Recording, and both of which applications are assigned to the assignee of this application, there is described and claimed an apparatus, method and medium for recording information in the form of minute thickness deformations in a thermoplas tic layer produced by establishing a charge pattern having a density distribution corresponding to the information to be recorded and rendering the thermoplastic sufiiciently liquid to be deformed and to retain the deformations upon cooling. Inasmuch as a preferred form of applying the electric charge pattern is with an electron beam, it is highly desirable to provide an apparatus in which the entire electron beam path is highly evacuated to avoid difficulties with arcing of the electrodes which generate and control the beam and to minimize electron scattering due to collision with gases which would otherwise be present in the beam path. As far as the operation of the electron beam writing apparatus is concerned, a good vacuum, for example, less than .1 micron is desirable. However, such a good vacuum effectively eliminates any cooling of the medium by gaseous conduction and accordingly greatly retards the cooling process, thus rendering difiicult the development of the recording medium in the same recording apparatus as the one where the exposure to the electron beam takes place. In accordance with an important aspect of the present invention a region of significantly higher pressure, in the order of 500-1000 microns or higher, is provided to enhance the cooling of the recording medium and this region is separated from the beam path by a path which substantially restricts the how of gases to render it relatively easy to maintain this significant pressure diflerential between the region of the beam path and the region where the cooling takes place. In other words, the recording apparatus involves a separation of the beam path from the cooling region by a sufficiently restricted gas flow path to maintain the desired pressure levels for the information writing by the electron beam and the enhanced cooling of the tape by gaseous conduction. A relatively small pressure of 500-4000 microns is sufficient to provide a very substantial increase in cooling rate, i.e., in the order of 10,000 times the cooling available at the high vacuum preferable for the electron beam path Without substantially increasing the problems of evacuation.

Accordingly, it is an important object of the present invention to provide an improved recording apparatus providing for the exposure of the medium to an electron beam in a high vacuum and cooling of the medium at a slightly higher pressure at which cooling by gaseous conduction is enhanced.

This and other objects of the present invention are accomplished in a specific embodiment of the invention by a recorder including two chambers or regions adapted to be maintained at different levels of pressure. In the first chamber the electron beam is formed, accelerated and modulated in accordance with the information to be recorded and impinged upon the recording medium in a manner to establish the information containing charge pattern as the medium is moved past the electron beam. In the first chamber also is mounted a supply of the recording medium and means for heating the medium before it moves past the information containing electron beam. The medium then passes through a restricted passage into the second or cooling chamber in which the medium cools sufiiciently to retain the deformations pro duced by the charge pattern on the heated recording medium before it is wound up on the storage reel. To enhance the cooling the recording medium passes along a circuitous path in this second chamber and also preferably passes adjacent extended areas of material having good heat conductivity and considerable heat storage capacity to facilitate the removal of the amounts of heat that are stored in the recording medium. This particular apparatus and method of developing and cooling the tape offers substantial advantages over prior recording apparatus. As in the prior recording apparatus, it is relatively easy to maintain the chamber in which the beam is generated and controlled at a very good vacuum since the exit passage of the beam to the recording area is relatively small even though it must be sui'ficient to permit the required movement of the beam transversely of the recording medium and also in the direction of the medium in those cases where defocusing of the beam in that direction is employed for control of the information to be recorded. Heating of the tape before recording which is disclosed as one of the alternatives in the aforementioned William E. Glenn, Jr. application, eliminates any slight cracks or defects that may be present in the thermoplastic layer prior to heating and in this way minimizes the distortion of the charge pattern that may otherwise be caused by these cracks and defects. The transfer of the heated tape to the chamber or region of higher pressure, namely in the order of 1000 microns permits relatively rapid cooling by gas conduction and in fact the rate of cooling approaches that attained at normal atmospheric pressure. Further objects and advantages of the invention will become apparent as the detailed description of the preferred embodiment of the invention proceeds, reference being bad to the accompanying drawing, and its scope to be pointed out in the appended claims.

In the drawing,

FIG. 1 is a plan view of a recorder with the cover open and embodying the present invention;

FIG. 2 is a sectional view taken along the line 22 of FIG. 1 showing the details of the heater structure;

FIG. 3 is an isometric view further illustrating the heater structure;

FIG. 4 is a sectional view illustrating the restricted passage from the chamber in which the recording takes place and the chamber where the cooling is accomplished at higher pressure, and

FIG. 5 is an isometric view of a short section of the recording medium which may be used to advantage in the recorder of the present invention.

Referring now to FIG. 1 of the drawing, the present invention is illustrated as embodied in a recorder including a vacuum-tight housing 19 having a cover 11 which when closed engages a vacuum-tight sealing gasket 12 which encircles the entire housing near the outer edge thereof as well as the walls separating the higher pressure cooling chamber 13 from beam generating and control region 14 and the heating and exposure chamber Chamber 14 houses the electron beam forming and control portion of the equipment, chamber 15, the tape supply, tape heating means and the station at Which the tape is actually exposed to the electron beam, while chamber 13 is the higher pressure chamber in which cooling is effected. The separation between the chamber 13 on one hand and chambers 14 and 15 on the other, is essentially complete except for the passage between chambers 13 and 15 through which the recording medium passes from chamber 15 to chamber 13.

A supply of the recording medium is provided in the chamber 15 on a supply reel 16. The medium, as shown in detail in FIG. 5, may include a backing or support layer 17, a transparent conducting layer 18, thin layer thermoplastic 19, which terminates short of the marginal portions of the tape in which openings are provided to provide for engagement with a driving sprocket. While the particular materials and construction of the tape are not, by themselves, part of the present invention and they may be made in accordance with the teachings of aforementioned Glenn application Serial No. 84,424, filed January 23, 1961, as a division of application Serial No. 8,842, filed February 15, 1960, a specific example of a tape suitable for use in the present invention is one in which the backing layer 17 is of an optical grade of polyethylene terephthalate which is available under the trade name of Cronar. The backing layer may be up to 4 mils in thickness, for example. The transparent conducting layer 18 may be formed in accordance with any of the known processes for forming a thin transparent conducting coating and may, for example, be accomplished by a copper iodide film. The thermoplastic layer which is the information storage layer may be a medium molecular weight polystyrene having a thickness, for example, in the range of .2 to 2 mils thick. The optimum thickness of the thermoplastic layer depends to some extent on the spacings of the information containing deformations and the thickness should be for best results equal to or less than the spacings between the adjacent depressions or deformations. The material from the reel 16 passes over idler pulleys 21 and 22 in close proximity to a radiant heater assembly 23, the details of construction of which are shown in FIGS. 2 and 3.

As illustrated, heater element 24 is in the form of a corrugated resistance extending generally parallel to one wall of the housing 11? having one end terminal 25 connected conductively with the housing 10 through conducting block 26. The other end of the heater is connected by a tap or terminal 27 to a conductive enclosing member 28 which is secured to the base of the housing It in insulated relation with respect thereto. As illustrated, this is accomplished by means of the insulating plate 29 and the holding and terminal studs 31 which pass through the housing 10 in electrically insulated and vacuum-tight relation with respect thereto. End plates or shields 32, secured to the ends of conducting block 26, confine the heat generated by element 24. It is apparent that the heater may be energized from a suitable source (not shown) having one terminal 33 connected to one of the studs 31 and the other terminal connected to the housing 10 which is maintained at ground potential as indicated at 34. After leaving guide pulley 22 the tape passes over a pair of rotatable flanges 35 which are lnoun e l, on the fixed post or shaft 3 6 which is slotted to 4 permit monitoring of the film as it passes the recording position by means of the magnifying lens assembly 37 and a prism 38 for reflecting light from the tape through an observation eye piece (not shown) which is suitably positioned in the cover member 11.

It will be understood that the thermoplastic layer 19 of the tape faces upwardly as it moves over the flanges 35 and having been rendered liquid, i.e., sufficiently liquid by the heater 23, to become deformed by the electrostatic charge is in deformable condition as it passes under the electron beam which emanates from the chamber 14. The tape then passes over an idler and guide pulley 39, a drive sprocket 4t), guide pulley 41, through an elongated restricted passage formed in the member 42 through which the tape passes from chamber 15 to the cooling chamber 13 which is maintained at a higher pressure. The tape then follows a circuitous path through the cooling chamber over pulleys 43-49, inclusive, and is wound up on the take-up reel 50 which is driven, but not positively, in accordance with the known tape handling art. Preferably the path of the tape over pulleys 4349 is adjacent a number of cooling members 51, 52 and 53 which are, as illustrated, in the form of elongated bars of aluminum, for example, which are secured to the bottom wall of the housing 11) in good heat transfer relation therewith. These members are good conductors of heat and also have considerable capacity for heat storage and assist in bringing the tape to a temperature at which the cooling of the thermoplastic layer is sufiicicnt to permit to to be rolled up on the take-up roll 50 without sticking or otherwise degrading the information containing deformations.

The cross-sectional View of FIG. 4 shows in more detail the nature of the restricted passage through which the tape is contained in its path from chamber 15 to the higher pressure chamber 13. This passage 56 may be formed in a body 54 of material which may, for example, be a solid plastic such as commercially available as Teflon, which is secured to the bottom wall of the housing It) to form effectively a barrier between chambers 13 and 15 except for restricted passage and which is provided on its upper edge with a gasket 58 for separating the two compartments. As illustrated, the passage through the body 5'7 is slightly greater transverse dimension in the region over the area of the tape which is coated with thermoplastic. The edges pass through the slightly narrower extensions of the opening 56 illustrated at 59. If the total thickness of the tape is in the order of 4 mils, the slots 59 may be approximately 8 mils, leaving 2 mils clearance on each side. The larger opening 56 provides a clearance, for example, of the order of 3 mils on the upper side, the side of the tape on which the thermoplastic layer is located and a slightly smaller spacing such as 2 mils on the bottom side.

In order to maintain the desired pressures within the apparatus, the housing 10 is provided with a number of ports which are connected to the vacuum system. The ports 6t) which may be connected with the diffusion pump opens into the chamber 14 housing the electron beam generating and control electrodes to insure the best vacuum in this region. A similar port 61 is provided in the high vacuum chamber 15. A port 62 may be provided in communication with the restricted slot 56 in the member 57 to help minimize the leakage from the higher pressure chamber 13 to the high vacuum chamber 15. Two ports 63 and 64 are illustrated as communicating with chamber 13. Port 63 may be connected with the vacuum system through a suitable shutoff valve and the port 63 may be provided as a controlled leak or port for admitting air or other gas into the chamber 13. Which one of these ports and in fact whether either of them is used, is determined by the system leakage and it is, for example, possible that there will be enough leakage to keep the pressure in the chamber 13 at the desired level, say in the order of 500 to 1000 microns, if neither porti63 or 64 is utilized. If not the pressure may be raised by a small and controlled leakage through port 63 or if the pressure tends to be too high, this port may be closed from communication to the exterior and a restricted passage provided from port 63 to the vacuum system.

In the description of the apparatus thus far, the beam forming and control apparatus for imparting a charge pattern to the medium for deforming it in accordance with the information to be stored has not been described. The particular form of this apparatus by itself is not a part of this invention. The apparatus may, for example, be the same as employed in my aforementioned copending application Serial No. 8,842, filed February 15, 1960, or of the type described and claimed in Patent 2,813,146, dated November 12, 1957, in which color information in the form of simultaneously applied diffraction patterns is impressed on a light modulating medium, specifically a liquid medium by modulating an electron beam in accordance with the color information. As schematically illustrated in FIG. 1., the beam generating and control apparatus may include an electron gun including a filamentary cathode 65, an apertured control grid 66, an apertured accelerating electrode or anode 67. The beam thus formed and accelerated passes between a pair of vertical deflection plates 68 and between the opposed electrodes of three pairs of generally cylindrical electrodes 69, 7t) and 71 and impinges the thermoplastic medium as it passes over the rollers 35.

The particular control imposed on the electron beam and as a result the particular type of information recorded on the medium as deformations thereof is not important to the present invention. The apparatus described, however, is siutable for impressing color television picture information on the medium in which case the energization of the electrodes may be in accordance with the disclosure of copending application Serial No. 119,712, filed .lune 26, 1961. For example, the horizontal deflection which determines the width of the tape which is subjected to the beam may be produced by a deflection voltage supplied to the pair of cylindrical electrodes 69. The electrodes 7-9 may also be supplied with the horizontal focusing voltage. The electrodes 70 are also employed for subjecting the beam to the voltage for velocity modulating the horizontal sweep in accordance with the color information of two color components, for example, red and blue. The electrodes 71 are supplied wtih the vertical focusing voltage, i.e., the voltage for focusing the beam in the direction of the tape travel. The electrodes 68, as described in that application, are energized by a voltage of relatively high frequencv and an amplitude which varies with the amplitude of the other color (green) to be recorded. This varies the charge density along the raster line in accordance with the amplitude of the green signal voltage. As will be understood, the movement of the tape is synchronized with the horizontal sweep voltage and the velocity of tape movement correlated with the sweep frequency to determine the vertical raster dimension. This arrangement produces two sets of orthogonally arranged light controlling deformations which may be used in conjunction with suitable optics such as those shown in the aforesaid application, Serial No. 119,712, to reproduce the color picture.

In the operation of the preferred embodiment of our invention described above, the system is evacuated and the heater element 24 energized so that, as the tape is driven past the heater and the recording station opposite the electron gun, it becomes heated to a state sufficiently liquid so that it is deformed by the electrostatic forces produced by the charge pattern established by the electron beam. As the deformed tape passes through the restricted opening 56, it passes from the chamber 15 to the chamber 13, the pressure increases, the cooling rate increases and as it passes through the circuitous path from the exit end of the passage 56 to the take-up reel St), in close proximity to the relatively massive heat storage and heat conducting members, the deformed surface is adequateiy cooled so that the film may be rolled up without any damage to the deformations. The present invention makes it possible to record and develop the medium all in a single recorder and thereby simplifies the recording and development of thermoplastic films of the deformed type.

It will be apparent that our invention in its broader aspects is generic to other specific apparatus for providing a region of higher gas pressure for cooling the recording medium lVVhllC facilitating the maintenance of the required vacuum in the region of recording. Other apparatus of this type which may be considered an improvement on the present invention is described and claimed in Day application Serial No. 139,461, led concurrcntiy herewith.

While a particular embodiment has been described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from our invention in its broader aspects and we aim, there fore, in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for recording information in the form of deformations of a recording medium comprising electron beam producing means for producing an information containing electron beam, a first vacuum chamber, heating means independently of said electron beam for heating said medium, means for transporting the medium to be recorded upon in said chamber past said beam producing means and said heater to produce deformations of the heated medium which vary in accordance with the information contained in the beam, a second vacuum chamber, a restricted passage interconnecting said first and second vacuum chambers, means maintaining said second vacuum chamber at a pressure above the pressure of said first vacuum chamber and above 500 microns and means transporting said tape through said restricted passageway into said second vacuum chamber whereby cooling is enhanced by the higher gaseous pressure encountered :in said passage and said second chamber.

2. Apparatus for recording information in the form of thickness deformations of a tape having a thermoplastic surface layer comprising electron beam producing means for producing an information containing electron beam, a heater independent of said electron beam for heating said thermoplastic layer, a first vacuum chamber, means for transporting the tape to be recorded upon in said first vacuum chamber past said beam producing means and said heater to produce deformations of the heated thermoplastic layer which vary in accordance with the information contained in said electron beam, a second vacuum chamber, a restricted passage interconnecting said first and second vacuum chambers, means maintaining said second vacuum chamber at a pressure above the pressure of said first chamber and above 500 microns and means transporting said tape through said restricted passageway and along a circuitous path in said second vacuum chamher.

3. Apparatus for recording information on a recording medium including a thermoplastic recording layer in the form of thickness deformations of the thermoplastic layer comprising a vacuum chamber, electron beam producing means in said chamber for producing an information containing electron beam, heating means in said chamber independent of said electron beam for heating said thermoplastic layer, means for transporting the tape to be recorded upon past said beam producing means and said heater to produce deformations of the heated thermoplastic layer which vary in accordance with the information contained in the beam, means defining a region out oor-2 '2 of pressure above 500 microns, means directing said heated medium along a path in said region, and means restricting the flow of gas between said region and said vacuum chamber.

4. The method of recording information in the form of deformations of a recording medium which comprises heating the medium in vacuum until the surface thereof is substantially liquid, subjecting the medium to an information containing eiectron beam in vacuum to establish a charge pattern thereon and resulting deformations thereof corresponding to the information impressed there- 5 fy the medium and preserve the deformations.

References Cited in the file of this patent UNITED STATES PATENTS Fisher Dec. 25, 1945 Groak Nov. 4, 1952 

1. APPARATUS FOR RECORDING INFORMATION IN THE FORM OF DEFORMATIONS OF A RECORDING MEDIUM COMPRISING ELECTRON BEAM PRODUCING MEANS FOR PRODUCING AN INFORMATION CONTAINING ELECTRON BEAM, A FIRST VACUUM CHAMBER, HEATING MEANS INDEPENDENTLY OF SAID ELECTRON BEAM FOR HEATING SAID MEDIUM, MEANS FOR TRANSPORTING THE MEDIUM TO BE RECORDED UPON IN SAID CHAMBER PAST SAID BEAM PRODUCING MEANS AND SAID HEATER TO PRODUCE DEFORMATIONS OF THE HEATED MEDIUM WHICH VARY IN ACCORDANCE WITH THE INFORMATION CONTAINED IN THE BEAM, A SECOND VACUUM CHAMBER, A RESTRICTED PASSAGE INTERCONNECTING SAID FIRST AND SECOND VACUUM CHAMBERS, MEANS MAINTAINING SAID SECOND VACUUM CHAMBER AT A PRESSURE ABOVE THE PRESSURE OF SAID FIRST VACUUM CHAMBER AND ABOVE 500 MICRONS AND MEANS TRANSPORTING SAID TAPE THROUGH SAID RESTRICTED PASSAGEWAY INTO SAID SECOND VACUUM CHAMBER WHEREBY COOLING IS ENHANCED BY THE HIGHER GASEOUS PRESSURE ENCOUNTERED IN SAID PASSAGE AND SAID SECOND CHAMBER. 